Hello, mods! I have a quick question about acceptable canon points/updating to a canon point!

In Tales of Zestiria, there's an epilogue scene in which a major time skip happens and focuses on one specific character (namely, Mikleo). There is enough canon (in both the game and some that can be pulled from a fan translation of the official light novel's epilogue) to make some educated guesses on how things have changed for the continent, though nothing specific like the names of any new countries. How much canon material would be needed in instances like this in order to apply from this point or update to it?